Oxidative coupling of methane at near ambient feed temperature

Abstract

Methods of performing a startup of an oxidative coupling of methane reaction to produce C2+ hydrocarbons are described. The methods can include incrementally varying startup parameters of the oxidative methane reactor and using the feed gas as a coolant such that high C2+ hydrocarbon selectivity is achieved.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of priority of U.S. Provisional Patent Application No. 62 / 457,119 filed Feb. 9, 2017, which is hereby incorporated by reference in its entirety.BACKGROUND OF THE INVENTIONA. Field of the Invention[0002]The invention generally concerns systems and methods for the production of C2+ hydrocarbons from methane (CH4) and oxygen (O2). In particular, the systems and methods allow for the use of parameters of reactant feed to a reactor to establish and maintain steady state operation.B. Description of Related Art[0003]Methane can be used to produce ethane and / or ethylene through the oxidative coupling of the methane (OCM) reaction. While extensive research and development has been devoted to this reaction, the reaction largely remains inefficient on a commercial scale. One of the key challenges is the high reaction temperature (typically greater than 750° C.) required to make the reaction proceed. The need for s...

AI Technical Summary

Benefits of technology

The invention solves problems with the OCM reaction by controlling the gas parameters in the reactor to maximize the conversion of methane to ethane and / or ethylene while avoiding damage to the catalyst. The reaction is ignited and operated in an autothermal state by supplying feed gas to the reactor at a low temperature to compensate for the heat generated by the reaction. This results in a cooling effect, as the feed gas is heated up to a higher temperature by the reaction.

Problems solved by technology

While extensive research and development has been devoted to this reaction, the reaction largely remains inefficient on a commercial scale.

One of the key challenges is the high reaction temperature (typically greater than 750° C.) required to make the reaction proceed.

This C—H bond strength makes methane less reactive and difficult to undergo oxidative conversion to form ethylene.

The excess heat from the reactions in Equations (III) and (IV) further exacerbate this situation, thereby substantially reducing the selectivity of ethylene production when compared with carbon monoxide and carbon dioxide production.

There are two important practical problems that have prevented the development of a commercially feasible OCM process: (1) the very large heat of reaction (Equations I-IV); and (2) the very high temperature required to initiate the reaction (typically 700-950° C.).

There is no commercially available liquid heat transfer fluid capable of operation at such high temperature.

Consequently, the only way to cool a reactor at this range of temperature is with very inefficient gas phase coolants (air, steam, or ethane, for example).

While this system can help with the energy input requirements needed for the OCM reaction, it relies on additional materials and a complicated catalytic bed design, which can be expensive and difficult to implement on a commercial scale.

Moreover, the methane conversion within each reactor must be limited to avoid runaway reaction and excessive catalyst temperature.

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